1. Field of the Invention
The invention relates to a process for the manufacture of zirconium oxide which is suitable for the manufacture of electro-ceramics from technical calcium zirconate.
In particular, the invention relates to the manufacture of zirconium oxide which, after conversion into cubic stabilized zirconium oxide, has a high electrical conductivity even at incipient red heat. It may therefore be used, for example, in the manufacture of ceramic test electrodes.
2. Description of the Prior Art
Zirconium oxide which is to be used for the manufacture of electro-ceramics must have a high purity. In particular, the zirconium oxide used for this purpose should contain less than 0.1 weight percent of Si0.sub.2, 0.05 weight percent of alkaline earth oxide, 0.05 weight percent of alkali oxide and 0.1 weight percent of TiO.sub.2. Otherwise, the physical properties required cannot be obtained.
It is possible to prepare a very pure zirconium tetrachloride by repeated sublimation in an atmosphere of hydrogen and to convert this in a known manner to the oxide. However, this process is too expensive for practical use.
The preparation of solutions of very pure zirconium oxychlorides by the repeated recrystallization of the oxychlorides is also known. This process is also too cumbersome and therefore too expensive for industrial application.
There is, therefore, a definite need for a process for manufacturing zirconium oxide suitable for the aforementioned purposes from an inexpensive raw material of technical purity.